1. Field of the Invention
The invention relates to a display device, and more particularly, to a display device including a backlight unit which uses light-emitting diodes as light sources.
2. Description of the Related Art
Liquid crystal displays (“LCDs”) are one of the most widely used types of flat panel displays. Generally, an LCD includes a pair of substrates having electrodes and a liquid crystal layer interposed between the substrates. In an LCD, voltages are applied to electrodes to generate an electric field. The electric field determines the alignment of liquid crystal molecules of a liquid crystal layer, thereby controlling the amount of light that passes through the liquid crystal layer. As a result, a desired image is displayed on the LCD.
Since LCDs are passive light-emitting devices, they require a backlight assembly unit which provides light that passes through a liquid crystal layer. Examples of light sources used in a backlight assembly include cold cathode fluorescent lamps (“CCFLs”) and external electrode fluorescent lamps (“EEFLs”).
In LCDs, light-emitting diodes (“LEDs”) have been widely used as light sources for a backlight assembly due to their superior color reproducibility and lower power consumption.
Backlight units are classified into direct-type backlight units and edge-type backlight units according to the position of light sources. In edge-type backlight units, a light source is disposed on a side surface of a light guide plate (“LGP”). Edge-type backlight units are applied mainly in relatively small LCDs such as laptop and desktop computers. Edge-type backlight units have superior light uniformity, have a long useful life, and enable LCDs to be thinner. However, edge-type backlight units have low optical efficiency since light emitted from a light source is lost as it passes through an LGP. In addition, in the case of large LCD panels, an LGP cannot be manufactured using a single frame.
As LCDs become larger, the development of backlight units has been focused on direct-type backlight units. In direct-type backlight units, one or more light sources are disposed under an LCD panel to provide light to the entire surface of the LCD panel. Since one or more light sources included in a direct-type backlight unit are disposed under an LCD panel, bright lines may easily be formed due to non-uniform luminance.